media: atomisp: get rid of most checks for ISP2401 version

There are lots of places inside this driver checking for
ISP2400/ISP2401 verison. Get rid of most of those, while
keep building for both.

Most of stuff in this patch is trivial to solve.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>